1. Field of the Invention
The present invention relates to a heat dissipation device for an electronic device, and particularly to a heat sink having at least a serpentine heat pipe.
2. Description of Related Art
Along with the continuous boom of computer industry, an electronic device, such as a central processing unit (CPU), is generating more and more heat. To ensure normal operation of the electronic device, accumulated heat must be removed away in time. Various heat sinks therefore have been devised to dissipate heat from electronic devices.
Conventionally, a typical heat sink conducts and dissipates heat by metal thermal conduction, and generally comprises a heat spreader for contacting the CPU for absorb heat therefrom and a plurality of fins provided on the heat spreader for dissipating heat. Limited to inherent characteristic of metal and cost consideration, heat conduction is not sufficiently fast and heat is mainly accumulated in the heat spreader. Heat dissipation capability of the heat sink does not satisfy the requirement of a high-powered heat-generating electronic device.
Nowadays, heat pipes, due to their excellent heat transfer performance, have been widely applied to heat dissipation of electronic devices. A heat pipe is a sealed metal pipe, with a low-pressure therein, in which a wick structure is formed and working fluid is filled. The heat pipe transfers heat from one end to the other by repeated phase change of working fluid between vapor and liquid states. A heat pipe has a high heat transfer performance due to fast circulation of working fluid and can transfer heat over a long distance.
Taiwan patent No. 532758 discloses a typical heat sink using heat pipes. The heat sink comprises a heat spreader for contacting a heat source, a plurality of parallel fins erecting on the heat spreader, and two U-shaped heat pipes attached to the heat spreader and extending through the fins to transfer heat from the heat spreader to the fins. The heat sink draws heat from the heat source via the heat spreader, one part of the heat is directly conducted upward to the fins; the remainder is indirectly transferred to the fins via the heat pipes. Generally, to maximize heat dissipation, the fins are made as large as possible; on the other hand, each heat pipe has a small cross-section size due to the limitations of manufacture cost and method; each of the heat pipes is brought to extend through a small circular hole defined in each fin and contact the fin. The contact between the heat pipes and the fins in the conventional heat sink is not adequate to offer a required heat transferring from the heat pipes to the fins. Vapors in heat pipes cannot sufficiently dissipate their heat to the fins through the contact between the fins and the heat pipes, whereby vapors in the heat pipes cannot totally condense into liquid and flow back to ends of the heat pipes thermally contacting with the heat spreader. Accordingly, utilization of heat transfer of the heat pipes is not high and heat dissipation of the heat sink is limited.
Therefore, it is desired to evolve an improved heat sink to overcome above-mentioned problems.